Seemingly ahead of his time, J.M.W. Turner (1775 -1851) was in fact very much of his times—times that, like the painter, kept leaping ahead via feats of imagination and technology. In Turner (Penguin Press, $35), her exhaustive biography of the prodigious British artist, Franny Moyle, whose previous subjects include Constance Wilde and the Pre-Raphaelites, traces the evolution of art and its marketing in the Georgian and Victorian eras from the traditional patronage system to the rise of auctions, galleries, and the independent artist. Turner was very much a model of the latter; proficient in drawings, watercolors, engravings, and oils, he had something to please everyone. His ambition matched his talent, and he was fiercely competitive, lobbying to be admitted to the Royal Academy when he was barely twenty (he was elected at age twenty-six) and identifying the strong points in rivals—then beating them at their own game. While Turner richly fulfilled the British appetite for scenes affirming the country’s “sense of power, solidity, continuity, and heritage,” he depicted Waterloo not as a national triumph, but as the epic slaughter of 40,000 killed in nine hours. Later, though demand for his realistic landscapes—product of an “encyclopedic” vision and compulsive sketching—remained high, Turner redirected his energies from the accurate depiction of a subject to the artist’s response to what he painted. He applied watercolor techniques to oils, exploring new ideas of truth in art. Critics weren’t ready, finding these works too vague, too bright, and too unfinished. But Turner, defended by the young John Ruskin, pressed on.